Migrate the callouts from using mutex locks to being mpsafe with
the locks being held by the callers.

Kill callout_drain() and use callout_stop().
There should not be zero length mbufs in socket buffers.  The code comes
from r1451, and thus can't be explained.  A patch with explicit panic()
here survived all tests.

Tested by:	pho
Sponsored by:	Nginx, Inc.
Add missing commas to .Xr.

MFC after:	1 month
Sponsored by:	The FreeBSD Foundation
Fix mdoc warning by removing empty lines.

MFC after:	1 month
Sponsored by:	The FreeBSD Foundation
In vfs_write_suspend_umnt(), if suspension cannot be established, do
not forget to restore write ops count when returning the error.

Reported and tested by:	pho
Sponsored by:	The FreeBSD Foundation
MFC after:	1 week
Fix mdoc warning.

MFC after:	1 month
Sponsored by:	The FreeBSD Foundation
Add OBJDUMP to sys.mk. The EFI loader uses it however without this it can
be set but empty.

Obtained from:	ABT Systems
Sponsored by:	The FreeBSD Foundation
Merge from projects/sendfile:
  Use sbcut_locked() instead of manually editing a sockbuf.

Sponsored by:	Nginx, Inc.
- Use NULL to compare a pointer.
- Use KASSERT() instead of panic.
- Remove useless 'continue', no need to restart cycle here.

Sponsored by:	Nginx, Inc.
sh(1): Add/improve information about exit status of commands.
Constantly indent struct pagerops.
Even better indent struct pagerops.
Use ${SYSDIR} as the reference pointer instead of specifying relative path directly.

Reported by:	jenkins via Olivér Pintér (on github)
Reference uefi(8) from i386 boot(8)

Suggested by trasz.

Differential Revision: https://reviews.freebsd.org/D1162
Cleanup trailing newlines noticed while looking for other issues.
Automate options INET/INET6 turning into MK_$opt_SUPPORT
correctly. Fixes if_gfe when building without INET6 and
simplifies if_gif's Makefile.

Sponsored by: Netflix, Inc
Remove mostly obsolete hint to disable LAPIC timers.

It is partially covered by new code and partially by new CPUs.

PR:		195016
Submitted by:	tobias.rehbein@web.de
MFC after:	1 week
Convert the callouts back to using mutexes.

I did this wrong - I should've included a state flag for each callout
to see if it was supposed to run or not.  I didn't do that.
Instead, just use mutexes anyway.

Suggested by: jhb
Use the standard powerof2() macro from param.h instead of a local one.

Pointed out by:	 jhb@
MFi386: r274398

  Move NFS and TFTP filesystems before the synthetic filesystems (bzip,
  gzip, and split).